The present invention relates to a power tool having air discharge windows, and more particularly, to a two-way rotatable power tool that has a radial fan for a cooling purpose.
FIG. 6 shows a conventional two-way rotatable power tool with a cooling fan. A two-way rotatable power tool is a power tool that can rotate both in the forward direction and in the reverse direction. The power tool includes a housing 103, and a motor (not shown) and a cooling fan 2 those positioned in the housing 103. The motor is provided with an armature and a stator. The cooling fan 2 is connected to the armature so as to rotate with the armature. The housing 103 has a part defining a fan chamber 105 for housing therein the cooling fan 2. Discharge windows 104 are formed in the housing part and are arrayed in a circumferential direction of the housing 103.
With the above-described configuration, when the motor is supplied with power, the cooling fan 2 rotates with the armature. The cooling fan draws air and generates air flow in an axial direction of the motor, so that heated components such as the motor can be cooled. The air is subsequently ejected from the discharge windows 104 in a direction indicated by an arrow 7.
One measure to improve cooling performance is to increase airflow rate by the cooling fan 2, and it is possible to increase the airflow rate by increasing the area of the discharge windows 104. If the area of the discharge windows 104 is excessively large, however, a user may get his fingers into the discharge windows 104 and touch the cooling fan 2 by mistake. Further, the strength of the housing 103 deteriorates if the area of the discharge windows 104 is excessively large.
In addition, as shown in FIG. 6, when the cooling fan 2 rotates in a rotational direction indicated by an arrow 6, air flow occurs in the direction indicated by the arrow 7. This causes vortex flows 8 that generate noise.
It is an object of the present invention to overcome the above-described problems and to provide an improved power tool capable of increasing an effective area of the discharge window without increasing an external or projection area thereof to thus increase an amount of air flow passing through the window.
Another object of the present invention is to provide such power tool capable of providing a smooth air discharging flow without vortex and noise.
These and other objects of the present invention will be attained by a power tool including an improved housing, a motor, and a cooling fan. The housing has a part defining a fan chamber and has outer and inner circumferential surfaces. The part of the housing is formed with at least one discharge window extending in a circumferential direction of the housing for allowing air to pass therethrough from the fan chamber to an atmosphere. The motor is disposed in the housing and includes an armature and a stator. The motor is rotatable in a first rotating direction and a second rotating direction opposite to the first rotating direction. The cooling fan is connected to the armature and is rotatable together with the armature. The cooling fan is disposed in the fan chamber. The at least one discharge window has a first side and a second side in opposition to the first side in the first and second rotating directions. The first side has a first slant wall portion at the inner circumferential surface to gradually reduce a thickness of the housing in the first rotating direction. The second side has a second slant wall portion at the inner circumferential surface to gradually reduce a thickness of the housing in the second rotating direction.